Notes

All arithmetic is performed modulo 2^n, where n is the number of
bits in the type. One non-obvious consequence of this is that Prelude.negate
should not raise an error on negative arguments.

For coercing between any two integer types, use
Prelude.fromIntegral, which is specialized for all the
common cases so should be fast enough. Coercing word types to and
from integer types preserves representation, not sign.

It would be very natural to add a type Natural providing an unbounded
size unsigned integer, just as Prelude.Integer provides unbounded
size signed integers. We do not do that yet since there is no demand
for it.

The rules that hold for Prelude.Enum instances over a bounded type
such as Prelude.Int (see the section of the Haskell report dealing
with arithmetic sequences) also hold for the Prelude.Enum instances
over the various Word types defined here.

Right and left shifts by amounts greater than or equal to the width
of the type result in a zero result. This is contrary to the
behaviour in C, which is undefined; a common interpretation is to
truncate the shift count to the width of the type, for example 1 <<
32 == 1 in some C implementations.